Do you know what your temps would get up to if you didn't crack it open? They can take "some" heat if it is sort of a one off situation. When trying to figure out the best course of action for a problem like this, I try and come up with the solution that would most closely resemble something that could happen in nature. So heat waves happen, it doesn't cause everything to die....but heatwaves also don't push temps to like 120 for the most part, so you need to be reasonable. Same line of thought if its better to have them have some extra dark or light time like shroomking outlined.
If you have a few days before your trip you could adjust when your night cycle happens, just adjust it an hour or so a day by adding or subtracting to your lights on period. You can't give them less than the 12 hours of dark (well you could); so you just have to adjust when the 12 hour dark period occurs. I bet you could even get by with adjusting the lights on period for just the one time and have it be a short day, then adjust back to what you are using now when you get home.
remember....its a weed, the stuff is very hardy compared to many plants.
